This invention relates generally to a die post assembly for supporting a thin metal panel in a position to allow a hemming implement such as a roller or die steel to flange and/or hem at least a portion of a marginal edge portion of the panel.
Die posts are used in hemming machines to support thin metal panels such as automobile body panels in positions that allow hemming or flanging implements such as rollers or die steels to flange and/or hem at least a portion of peripheral edges of the panels.
Many die posts are of all-metal construction and are made by casting hardenable iron. In a die post of this type, hardenable iron is cast into a shape that includes a support surface. The support surface is shaped to complement and support a portion of a metal panel while allowing a marginal edge portion of the metal panel to be flanged, hemmed, or roll formed to a finished configuration. Such die posts also generally include a bearing region comprising at least a portion of an outer marginal portion or peripheral edge region of the die post support surface. The bearing region supports a portion of a metal panel overlying the bearing region against deformation as the marginal edge portion of the metal panel is flanged or hemmed. However, cast metal die posts are quite massive and cannot be easily moved from one location to another without special lifting equipment. Neither can such die posts be manually lifted into position during assembly in a hemming apparatus. Because of their weight, cast die posts require heavy support members to support them in a hemming apparatus. Moreover, cast metal lacks dimensionally stability after casting and must be set aside for approximately six weeks before machining to within final tolerances.
Some die posts constructed for low-volume applications such as prototype dies are all-plastic in composition. Such die posts may be constructed by cutting and bonding together filled urethane tooling planks to form a rough approximation of the desired shape of a support surface. The support surface is then machined to a desired complementary shape. As with cast metal die posts, a bearing region comprises an outer portion of the support surface of the die and supports a portion of a metal panel overlying the bearing region against deformation as adjacent portions of the panel are being stamped or bent to a desire shape. However, die posts having plastic bearing regions are unable to support a portion of each of a series of metal panels against deformation over a large number of cycles without flowing due to heat or pressures generated in an edge flanging or hemming process.
What is needed is a die post that can be easily moved from one location to another without special lifting equipment and can be lifted into position using a fork truck or electric hoist during assembly in a hemming apparatus. It is also desirable that such a die post be supportable in a hemming apparatus without heavy support members. Still further, it is desirable that such a die post be more dimensionally stable than cast iron while retaining the capability to withstand a large number of cycles.
According to the invention, a die post assembly is provided for supporting a thin metal panel in a position to allow a hemming implement such as a roller or die steel to flange, pre-hem or hem a marginal edge portion of the panel. The assembly includes a die post support surface configured to support a metal panel to be flanged, pre-hemmed or hemmed. The die post support surface is configured to allow a marginal edge portion of the metal panel to extend beyond an edge of the die post support surface when the die post is used to support a metal panel during flanging operations. The die post support surface includes a bearing region disposed adjacent the edge of the die post support surface and is configured to support an overlying portion of the panel adjacent the marginal edge portion of the metal panel against deformation as the marginal edge portion of the metal panel is bent in a flanging, pre-hemming or hemming operation. The assembly also includes a panel support element comprising a first material and including an inner region of the die post support surface.
Unlike the prior art, the assembly also includes an edge member supported on the panel support element. The edge member includes the bearing region of the die post support surface and comprises a second material more durable than the first material.
According to another aspect of the invention, a hemming die apparatus is provided for supporting a thin metal panel in a position to allow a hemming implement such as a roller or die steel to flange or hem at least a portion of an edge of the panel. The hemming die apparatus comprises a die post configured to support a metal panel to be flanged or hemmed in a flanging or hemming operation. The apparatus also includes a die post support assembly configured to removably support the die post for pivotal motion between a generally upright installation position and a work position for hemming or flanging a thin metal panel supported on the die post. The die post may, according to the invention, be installed and removed in a generally upright (vertical or slightly inclined) position rather than being lifted off of or onto the support assembly in the prone or generally horizontal position.
According to another aspect of the invention, a method is provided for making the die post assembly. The method includes providing a panel support element comprising a first material, providing an edge member comprising a second material more durable than the first material and assembling the die post by supporting the edge member on the panel support element.
Objects, features and advantages of this invention include the ability for the die post to support a series of metal panels in a flanging, pre-hemming or hemming operation over a large number of cycles without flowing or deforming the bearing region of the die post support surface as a result of such factors as heat or pressures generated in a hemming or flanging process; reducing effort required to move the die post and structural requirements of the die post support assembly and reducing effort required to install and remove die posts on a die post support assembly.